xargs defaults to all whitespace because it was designed to get around the problem of short argv lengths (like, I'm talking 4k or less on older Unix-y systems,

xargs defaults to all whitespace because it was designed to get around the problem of short argv lengths (like, I'm talking 4k or less on older Unix-y systems, sometimes as low as 255 bytes). So the defaults went with principle of least surprise, pretending it's like a very long args list that you could theoretically enter at the shell, including quotes. You could, for example, edit the args list in vi and line split / indent as you please but not impact the end result.